I run the Brown Dog mounts and brackets as well. At about 220k I hit a pothole in an intersection and sheared off all 3 of the bolts on the passenger side of the block. I only managed to get 2 of the 3 bolts out of the block so I decided to get the brackets. I landed up getting the ones with poly bushings and its not *too* bad. The Jeep does shake like an epileptic and the antenna is always wiggling at idle, and from inside the cab it sounds like a diesel truck, but I know the engine will never move again! Personally, I dont mind it at all, but I do get some interesting looks when sitting at stoplights.
Like mcguyver_xj was saying; go rubber if you dont want vibrations and poly if you dont mind em.
If you have more questions, maybe email the guys who run Brown Dog? They would be a lot more help that me I suppose